The present invention relates to a cellular phone and a mobile switching controller, and more particularly to a cellular phone and a mobile switching controller for use in an in-office internal phone system.
WOS (Wireless Office Service) systems have been known as a system using a cellular phone as an in-office internal phone. A WOS system is designed such that a base transceiver subsystem (BTS) for the WOS system is installed in a limited space such as in an office or in a school to be connected to a private branch exchange (PBX), and a cellular phone is registered in the WOS system, thereby using the cellular phone as an internal phone within a communication service area of the WOS system and enabling connection to the in-office internal phone in response to a transmission of an extension number from the cellular phone. In the WOS system, a caller, who exists within the service area of the WOS system, can input a dedicated special number at a position before the extension number and then transmit it to call a partner, who is an object of connection, through a base transceiver subsystem of the WOS system irrespective of whether the partner exists inside or outside the WOS system service area. On the other hand, in a case where the caller exists outside the WOS system service area, the caller first makes a telephone call to a general pilot number of that company and, after the automatic answering “dial an extension number” from the PBX, dials the extension number for connection, thus making a calling access to the cellular phone corresponding to this extension number (see “Best Plan for Phone Number”, NIKKEI COMMUNICATIONS, NIKKEI BP, May 15, 2005, Page 50, FIG. 8).
JP-A No. (HEI) 06-062455 and U.S. Pat. No. 5,379,339 disclose a wireless phone apparatus having a ROM for storing an extension call number and an outside-line call number for a cellular phone in a state associated with each other. This wireless phone apparatus is made to output a DTMF (Dual Tone Modified Frequency) code corresponding to the outside-line call number stored in the aforesaid ROM from a DTMF code memory to an audio codec unit when a cellular phone under an extension call specification by a key operation in a key inputting unit is out of calling area. Thus, a DTMF signal corresponding to the outside-line is outputted from a line interface unit to achieve a calling access to the cellular phone.
Moreover, for connection to an internal phone from the interior of the WOS system service area, the caller can put a dedicated special number at a position before a connection-accepting side extension number and transmit it. Still moreover, for connection to an internal phone from outside the WOS system service area, the caller needs to once make calling through the outside line to establish connection to the PBX and then input an extension number after an automatic exchange answer message from the PBX. It is necessary to use numbers properly between the interior and exterior of the service area, which incurs a disadvantage of complicating key operations for extension connection.
In a case where a caller stays within a service area, the technique disclosed in JP-A No. Hai 06-062455 or U.S. Pat. No. 5,379,339 realizes a method of, even if a connection partner is out of a system service area, establishing connection through the same calling operation as that to be conducted when the connection partner stays within the service area. However, no consideration is given to a calling method to be carried out when the caller is out of the service area.